Abstract
The first nuclear bomb detonation on Earth involved a plutonium implosion-type device exploded at the Trinity test site (33°40′38.28″N, 106°28′31.44″W), White Sands Proving Grounds, near Alamogordo, New Mexico. Melting and subsequent quenching of the local arkosic sand produced glassy material, designated “Trinitite”. In cross section, Trinitite comprises a thin (1–2 mm), primarily glassy surface above a lower zone (1–2 cm) of mixed melt and mineral fragments from the precursor sand. Multiple hypotheses have been put forward to explain these well-documented but heterogeneous textures. This study reports the first quantitative textural analysis of vesicles in Trinitite to constrain their physical and thermal history. Vesicle morphology and size distributions confirm the upper, glassy surface records a distinct processing history from the lower region, that is useful in determining the original sample surface orientation. Specifically, the glassy layer has lower vesicle density, with larger sizes and more rounded population in cross-section. This vertical stratigraphy is attributed to a two-stage evolution of Trinitite glass from quench cooling of the upper layer followed by prolonged heating of the subsurface. Defining the physical regime of post-melting processes constrains the potential for surface mixing and vesicle formation in a post-detonation environment.
Highlights
Physical effects of nuclear blasts are recorded in post detonation material
Size distributions of small vesicles are a viable method of distinguishing original surface direction in cross section
Continued degassing of the molten desert sand would promote near-surface mixing by vesiculation, in addition to increased mobility between phases of different densities [2]
Summary
Physical effects of nuclear blasts are recorded in post detonation material. The melting temperatures (ranging between ~700 and ~1200°C) of nearby surficial geologic materials at White Sands were generally exceeded by nuclear blast heat, with some variability with distance from ground zero. The Trinity nuclear test fireball temperature exceeded 8000 K, creating a vapor cloud comprising the bomb, steel tower, and surrounding desert sand [1,2,3]. Nuclear post-detonation materials, such as Trinitite, are hand-sample scale records of atomic blasts. Relict quartz grains are abundant in Trinitite, transformation to α-quartz is observed [4,5]. The brief, 3.1-second high-temperature blast was followed by cooler air brought in by the rising heat, which likely quench-cooled the surface melt [2]. The intact crystal boundaries of in PLOS ONE | DOI:10.1371/journal.pone.0163516 September 22, 2016
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